I have commented on this issue previously: More on groundwork. Now the 1st Circuit seems to want to get tougher with prosecutors.
First Circuit Once Again Criticizes The Use Of Law Enforcement “Overview” Testimony.
After prior admonitions, First Circuit warns prosecutor that failure to avoid the problems in using an “overview” witness may result in possible sanctions or disciplinary action, in United States v. Flores-De-Jesus, _ F.3d _ (1st Cir. June 18, 2009) (No. 06-267, 06-2670, 06-2671) (Torruella, Lipez, and DiClerico (DJ)).